Abstract
Cystic dilatations of the cystic duct which are suggested as type VI biliary cysts are very rare and many of them go unrecognized or are confused with other cysts until the operation although they are obvious on imaging studies. They can present with fusiform or saccular dilatations and can be accompanied by common bile duct dilatations. It is important to identify these cysts as they share the same characteristics as the other biliary cyst types and can be complicated with malignancy. We herein present a very unusual case of a cholangiocarcinoma arising from a type VI biliary cyst in a 58-year-old female patient and review the literature. The patient presented with jaundice, weight loss, and abdominal pain. On imaging, the cystic duct and common bile duct were fusiformly dilated and had a wide communication. There was a mass filling the distal parts of both ducts. The patient was urgently operated on after perforation following ERCP. Histopathology was compatible with a type VI biliary cyst and an associated cholangiocarcinoma.